This present invention relates to an improvement in medical and scientific devices for measuring physical attributes of muscles, and more particularly to measuring muscle tone, compliance, and paresis. The is accomplished by incorporating a translating probe or prod which is in communication with one or more transducers which act to quantify the force applied to skin and underlying tissues (e.g., muscle) and the amount of tissue displaced thereby. Results are stored, analyzed, and compared against previous results via a computer interface.
Health-care personnel, generally within the specialties of neurology, neurosurgery, rehabilitation, and physical medicine, evaluate and treat patients who have had or currently have various disabilities as a result of injury or disease to muscle or the nervous system, or a combination of both thereto. A common sequelae to many neurological conditions are pathological changes in muscle tone, compliance, and strength--all of which contribute to a disorder known as the spastic condition. Generally speaking, muscle tone may be described as the background tension within a muscle at rest. Clinically, muscle tone is typically tested by passively moving a patient's limb into flexion and extension and subjectively monitoring the amount of resistance offered by the muscle during the movement. Attempts have been made to lessen the subjectivity of this form of testing. The Ashworth scale is one such attempt. In this regard, an ordinal scale ranging from 1-4 is used to assess muscle tone. The scale is the clinical gold standard used for muscle tone assessments but it remains a less than optimal test because of poor test-retest reliability, poor inter-tester reliability, and a clustering effect (i.e., most patients receive a similar rating regardless of level of severity of disability).
Muscle compliance basically is the amount of force produced by a muscle in response to lengthening of that muscle; it is the inverse of elasticity--the intrinsic quality of a muscle that resists stretch. Muscle compliance testing is typically done with complex, specialized, and expensive laboratory equipment. As such, it is not a widely used clinical testing procedure.
Muscle strength is the amount of force that can be generated by a muscle. The amount of weight an individual can lift has always been equated with muscle strength. Pain or patient intervention, however, can interfere with an accurate assessment of an individual's muscle strength. Increasingly, muscle strength is being tested with various computerized machinery or with surface electromyography. Paresis is associated with muscle strength in that it is the weakness manifested by an individual during muscle contraction.
Spasticity in an individual is a complex combination of overall muscle condition and, therefore, is a difficult condition to define with a great detail of specificity. Basically, spasticity encompasses combined changes in muscle tone, muscle compliance, and muscle strength. A person suffering from spasticity generally experiences an increase in muscle tone and muscle compliance while exhibiting a decrease in muscle strength.
A reliable, valid, fast, easy, and relatively inexpensive means to quantify and analyze each of the conditions described above has proved to be rather elusive.
There are also numerous protocols currently in use that are employed to decrease spasticity and alter muscle tone. Quantifying the effectiveness of these protocols, however, has also been difficult because of the lack of an appropriate test instrument which can quantify pre- and post-treatment outcomes.
Our present invention is a reliable device which is capable of quickly and effectively measuring and quantifying muscle tone, muscle compliance, and muscle strength. The present invention is a hand-held electronic device that can be interfaced with a computer so that measurements may be stored and analyzed with, and against, other measurements previously taken and recorded. It is a non-invasive, painless, easy-to-use device which provides accurate, reliable, and reproducible results. In operation, the device is placed on a patient's skin. A probe is gently pressed downward on the skin surface. The probe does not penetrate the skin but merely pushes against the skin. The measurements taken by the present invention includes the amount of deformation (skin displacement) which results when a given unit of force is exerted on the underlying muscle, first, in its relaxed (resting) state and, second, in its maximally contracted state. Values derived from a rested state provide an accurate assessment of muscle tone and muscle compliance. Values derived from a contracted state provide an accurate assessment of muscle strength. The differences between the two sets of values when graphed linearly reflect slopes whose differences represent an assessment of the severity level of the person's spasticity.
Quantifying the spastic condition would have a considerable economic impact for the health-care industry. For instance, cerebral vascular accidents (CVAs--commonly referred to as `stroke`) affect over 500,000 Americans annually. Approximately one-third are permanently disabled. Rehabilitation costs for those disabled exceeds $25 billion annually. Spasticity and muscle tone alteration almost always follow a stroke. To date, there are numerous treatments for the condition. Such treatments include various pharmacological agents, surgeries such as dorsal root rhizotomies (surgical procedure to reduce muscle tone and, thereby, spasticity), casting the spastic limb, and various physical therapies. Because there is no easy and reliable method to quantify spasticity, treatment protocols tend to rely on trial an error rather than any proven effectiveness.
The ability to quantify one's spastic condition will take on increased significance as different drugs are developed to mimic specific neurotransmitters within specific neural pathways. Attempts are underway to identify the dysfunctional neural pathways associated with stroke and other neurological diseases. dorsal root rhizotomy is gaining in popularity although the longterm effect is uncertain and may not be a real cure. Currently there is no accurate and reliable manner or instrument to properly assess spasticity. In today's world of managed health care, the emphasis is clearly on effective treatment. The present invention paves the way for effective treatment regimens.
Devices based on the concept of comparing force and displacement measurements exist but they tend to be large, cumbersome devices, and lacking in requisite accuracy. One such similar device can be found in U.S. Pat. No. 3,133,355 issued to Gordon on May 19, 1964. It, however, relates only to measuring muscle tone (resting muscle tension). Although suited for the intended purpose, it is a rather intrusive device, cumbersome to operate in that it requires precise positioning, and is not capable of measuring muscle compliance, measuring muscle strength, or recording and analyzing such data as collected. Other instruments include that addressed by Fischer's tissue compliance meter. This instrument uses a force gauge which is pressed into the muscle at a known force and measures the depth of penetration with a spring gauge. It requires 2-3 kg (kilograms) or more of force and is used to measure depths at 1 kg-force increments from 1-5 kg. All these prior art instruments lack precision and lack the functional ability to measure all three conditions, to record the results, and to analyze the results against previous results. In short, a need existed for a device and method which could quantify muscle tone and would permit for repeated measurements with precision and further permit comparisons of such measurements over time. The present invention employs highly accurate transducers aligned for accuracy and to prevent time-lag between transducer recordings. Prior art devices use spring gauges which are inherently inaccurate and show fatigue and increased inaccuracy over time.
The present invention represents a unique combination of newly developed structure and process which, together provide for accurate and reliable assessments of spasticity, muscle tone, muscle compliance, and muscle strength. Analysis of the measurements may be performed by any conventional computer, attachable to the device, which record the results and, through any conventional output device (monitor, printer), provides the results to a health-care practitioner immediately.
Accordingly, several objects and advantages of the present invention are to:
a. provide for an economical, yet accurate apparatus for measuring muscle conditions; PA1 b. provide for an apparatus which is capable of measuring force and depth relative to that force when applied to a muscle; PA1 c. provide for an apparatus which is simple to use; and PA1 d. provide for an apparatus that is capable of multiple measurements of force/depth, recording such measurement, and storing such measurements for future use and comparison relative to therapy and treatment effectiveness.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.